A variety of communication services have been spread due to widely-used information processing and information communication techniques, and particularly communication systems including cell phones have been remarkably developed. At present, for 3GPP (Third Generation Partnership Project), the global standard of the third generation (3G) mobile communication system “IMT (International Mobile Telecommunications)-2000” defined by ITU (International Telecommunication Union) is being standardized. One data communication specification “LTE (Long Term Evolution)” defined by 3GPP is a long-term advanced system directed for the fourth generation (4G) IMT-Advanced, and is called “3.9G (super 3G).”
For example, a communication system having a base station accommodating a terminal has a problem of how to reduce consumed power of the terminal. In particular, it is important to reduce consumed power when the terminal is not making communication. Intermittent reception is widely known as one method for solving the problem. Intermittent reception is a communication control system for keeping a period for receiving a signal from a communication network at minimum while the terminal is not making communication, and for powering off a receiver during the remaining period thereby to reduce consumed power. For example, a cell phone powers on the receiver for receiving essential information such as paging information for a communication operation from a base station and powers off the receiver during other period. For the above 3GPP, an outline of the intermittent reception as DRX (discontinuous reception) is described (see Non-Patent Document 1, for example).
There are proposed a method for dividing terminals into a plurality of groups, shifting a cycle of DRX per group, and reducing a rate of the ON state in each cycle of DRX thereby reducing consumed power (see Patent Document 1, for example), and a method for using DRX with different cycles depending on a time (for example, daytime and nighttime), thereby further elongating the cycle of DRX (see Patent Document 2, for example).
A communication network is widely used in other than terminals directly used by persons for communication such as meters, automatic venders and electronic advertisements in addition to normal terminals directly used by persons such as conventional cell phones and PC (personal computer). In the following, the communication which is not directly used by persons is called MTC (Machine Type Communication), and a terminal which is not directly used by a person for communication is called a MTC terminal.
For MTC, a communication frequency necessary for the MTC terminal is relatively lower than the normal terminals (such as once a day, once a week or once a month), and the amount of data used for communication at a time is not large. On the other hand, it is expected that remarkably small consumed power is needed for the MTC terminal.
When the cycle of DRX is simply made longer for reducing consumed power, the terminal can fail to receive system information or paging information transmitted from the communication network. Thus, the terminal intermittently operates while securing a chance to accurately receive information from the communication network (the base station), thereby to further reduce consumed power of the terminal.
It is assumed that the communication of the MTC terminal is made according to a communication schedule desired by users inside the communication network or users outside the communication network. In this case, the communication network (the base station) needs to grasp the communication schedule and reflect it on the DRX setting in order to meet the conditions of the user-desired communication schedule.